Television receiver



Oct. 20,1953 (3. L. FAUDELL TELEVISION RECEIVER Filed July 24, 1948crass pa szcow.

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r n flw mm? v W a Patented Oct. 20, 1953 TELEVISION RECEIVER CharlesLeslie Faudell, near Stoke Poges, England, assignor to Electric &Musical Industries Limited, Hayes, England, a company of Great Britain 7Application July 24, 1948, Serial No. 40,530 In Great Britain July 31,1947 strength'of the reflected signals approaches the I strength of thedirectly received signals. The frequency of fading lies mainly in therange between 30 cycles per second and one cycle in several seconds.

It is the object'of the invention to provide a television receiverwhereby the effect of interfering reflected signals is rendered lessnoticeable in the reconstituted picture. 1

According to the invention there is provided a television receivercomprising a signal channel adaptedto'pass signals of the field andhigher frequencies but to attenuate signals of lower than fieldfrequency down to a frequency of at least 1 cycle per second and totransmit the D. C. component of the signals, thereby substantially toreduce fading of the mean brightness of the reconstituted picture due totelevision signals reflected from moving objects.

In order that the said invention may be clearly understood and readilycarried into effect, the same will now be more fully described withreference to the accompanying drawing, in which:

Figure 1 shows part of a television receiver having a signal channelaccording to one form of the invention,

Figure 2 shows part of a television receiver having a signal channelaccording to another form of the invention,

Figure 3 is a graph showing the attenuation at various frequencies dueto a specific signal channel of the form shown in Figure 2, and

Figures 4 and 5 show parts of television receivers having signalchannels according to further forms of the invention.

Referring to Figure 1, reference numeral 1 indicates an electrondischarge amplifying tube, included in a signal channel having inputterminals 2 and 3 and output terminals 4 and 5. Television signals withtheir D. C. components are applied to the input electrodes of tube l viaterminals 2 and 3, and the amplified signals are fed to output terminals4 and 5. The anode of tube l is con nected via resistors 5 and i topositive H. T. terminal 9, and the junction of resistors 6 and I isconnected to ground via a capacitor 10. The

8 Claims. (01. 178-73) r a I 2 n anode of tube I is coupled via acapacitor"! output terminal 4 and the junction of resistors 6 and I isconnected to ground via a capacitor Hi. The anode of tube I is coupledvia a capacitor l i, to output terminal i and the junction of resistors5 and I is connected to terminal 4 via a resistor I2. Between terminals4 and 5 is connected a resistor it which with resistor I2 forms apotential divider so that terminal 4, which may for example be connectedto the control electrode of the cathode ray tube of the receiver, ismaintained at an appropriate potential.

Capacitor ll provides anA. C. path between the anode of tube l andterminal t, and with'resistor l3 forms a filter circuit which transmitsthe picture signals and the line and field synchronising pulses, butattenuates signals of frequencies' lower than that of the fieldsynchronising pulses. For example, in a receiver employing interlacedscanning with 50 frames per second, said filter circuit is arranged totransmit signals at and above 50 cycles per second but to attenuatesignals of a lower frequency, the attenuation being substantial at andbelow a frequency of 30 cycles per second.

Resistors B and I2 provide a D. C. path, in parallel with the A. C.path, between the anode of tube l and terminal 4, and resistor l andcapacitor it form a filter circuit such that signals having a frequencyabove 1 cycle per second are attenuated. Said filter circuit may be suchfor example that signals of a higher frequency than 0.5 per second aresubstantially attenuated, whilst the D. 0. component and slow variationsthereof are transmitted. The signal channel thus substantiallyattenuates signals at frequencies in the range of 0.5 to 30 cycles persecond.

Referring now to Figure 2, which shows another form of coupling circuit,the anode of tube l is connected to positive H. T. terminal 8 via anoderesistor 8, and to output terminal 4 via capacitor II, which is shuntedby resistors It and iii in series, the junction of resistors Hi and 15being connected to ground via a resistor I6 and a between the anode oftube I and output terminal 4, and with resistor 15 forms a filtercircuit producing negligible attenuation and phase shift of ignals atand above the field frequency, e. g., 50 cycles per second, butattenuating signals of lower frequency, the attenuation increasing as(see British patent specification No. 505,899).

about 60 per cent only of the D. C. component being retained.

The effect of the filter circuits is shown n Fi ure 3 whereinattenuation is plotted against f requency for a signal channel accordingto Figure Curve It shows the pass characteristic of, the A. C. path andcurve I9 shows that of the D. C. path. The attenuation due to filtercircuit I I, I alone is negligible at and above 50 cycles per second,but is 10 dbs at 10 cycles per second and dbs at 1 cycle per second.The. attenuation due to filter I4, Ii alone is 8 dbs at of a cycle persecond and 20 dbs at 1 cycle per second. The combined effect of thefilter circuits is shown by the full-line curve 20, which shows that thepeak attenuation occurs in the range of 1 to 3 cycles per second and isof the order of 20 dbs. The

result is a very noticeable-reduction of the objectionable fading of themean brightness of the viewed image.

Referring now to Figure 4, television signals, including the D. C.component, are applied to terminals 2 and 3, resistor 2I representingthe output load of the preceding stage, and are fed to the inputelectrodes of tube I via a network comprising a capacitor 24 which isshunted by resistors 22 and 23 the junction of which is connected toground via capacitor- 215. The anode of tube I is connected'to positiveH. T. terminal 9 via resistors 6 and 'I" the junction of which isconnected to ground via capacitor It. The anode of tube I is connectedto output terminal 4-v-1a capacitor I I and shunt resistor 12, and aresistor I3 is connected between output terminals 4 and 5. Resistors 22and 23 form a D; C. path between terminal 2 and the control electrode oftube I, an A. C. path being provided by capacitor 24. Capacitor IIprovides an A. C'. path between the anode of tube I and terminal 4, andwith resistor I3 forms a filter circuit which transmits signals at andabove cycles per second but attenuates signals of a lower frequency. TheD. C. path between terminals 2 and 4 includes two filtercircuits one ofwhich is in the output circuit of tube I and is constituted by resistorI and capacitor- I0, and the other of which is in the input circuit totube I and is constituted by resistor 22 and capacitor 25'. The totaleffect of said filter circuits in the D. C. path is such that signals ofa frequency above 1 cycle per second are attenuated but signals of alower frequency are trans mitted to output terminals 4 and 5 viaresistor I2, whereby the D. C. component andslow variations thereofappear at terminals 4, and, 5..

In the signal channel of Figure 4 two filter circuits are provided atdifierent parts, of the D. C. path. If desired, a single filter circuitmay arranged to operate a a cathode follower.

4 be provided in the part of the signal channel preceding tube I, filtercircuit I, I0 being omitted and filter circuit 22, 25 being such thatsignals of a frequency below 1 cycle per second are transmitted butsignals of a higher frequency are attenuated. In this case however,there will be some loss of D. C. component, since the D. C. boostafforded by circuit 7, I0 and compensating for the D. C. loss inresistors I2, I3 is absent. In

I such an arrangement the filter circuits which are respectively in theA. C. and D. C. paths are at different parts of the signal channel.

Figure 5, shows a signal channel in which the A. C. path is providedwith two filter circuits at different parts of said path. Televisionsignals are applied to the input electrodes of tube I via terminals 2'and 3, resistor 2I again representing the, output. load of a precedinstage, and the anode of tube I is connected to positive H. T. terminal 9via resistors 6 and I, the junction of which is connected to ground viacapacitor I0, resistor E. and capacitor I0 forming a filter circuitwhich transmits signals of a frequency below 1 cycle per second butattenuates signals of a higher frequency. The D. C. component of theoutput, from tube I is. fed to output terminal 4 via resistor I2, whichwith resistor I3 between output terminals 4 and 5 provide apotentiometer circuit as described in connection with Figure l. The A.C. path between the, anode of tube I and output terminal 4. comprises anelectron dis,-

charge tube 25, a capacitor 21 connected between.

the anode of tube I and the control electrode of tube 26, and acapacitor 3i connected between the cathode of tube 26 and terminal 4.The cathode of tube 28 is connected to ground via resistors 29 and 30,anda resistor 26 is connected between the control electrode of tube 2 6and the junction of resistors 25 and 30. Tube 26. is thus Capacitor 2'!and resistor 28 form a first filter circuit in the A. C. path, andcapacitor 31 and resistor I3 form a second filter circuit in said. path,the. total efiect of said filter circuits in said path being to provideattenuation of signals be? low the field frequency.

A signal channel according to the. invention may be. arranged in anysuitable part of the circult of the television receiver, for example be.tween the final amplifying tube and the cathode ray tube, as described,or between the detector tube and the next following tube of the circuit.

What I claim is:

l. A television receiver including a picture re.- constitnting deviceoperating at. line and field frequencies, a, signal channel connectingthe signal input of said receiver to said deyice, said channel includingan electron discharge tube having a, cathode, a control electrode and ananode, an alternating current path connected to said tube for passingsignals of the field and higher frequencies, a direct current pathconnected to said tube for passing signals of zero frequency, saidalternating. current path and; said direct current. path comprising apair of resistors in series between said anode. and a. positive, sup:ply terminal, acapacitor connected between the junction of saidresistors and ground. a second pair of resistors. and said otherelectrode of said second capacitor, said, first-mentioned capacitor andthe resistor connected to said positive supply terminal beingproportioned to serve as a filter to attenuate signal components at afrequency higher than 1 cycle per second, and said second capacitor andsaid third resistor being proportioned to serve as a filter to attenuatesignals at frequencies below the field frequency, whereby on theapplication of signals having D. C. and A. C. components to said cathodeand control electrode signals are obtained between the ends of saidthird resistor in which components at frequencies between the fieldfrequency and a frequency of 1 cycle per second are attenuated.

2. A television receiver comprising a signal channel including anelectron discharge tube having a cathode, a control electrode and ananode, a first resistor, said cathode being connected to ground and saidanode being connected to a positive supply terminal via said firstresistor, second and third resistors connected in series between saidanode and ground, a first capacitor connected between the junction ofsaid second and third resistors and ground, and a second capacitor and afourth resistor connected in series between said anode and theungrounded electrode of said first capacitor, said second resistor andsaid first capacitor being proportioned to serve a a filter forattenuating signals having frequencies above 1 cycle per second, saidsecond capacitor and fourth resistor being proportioned to serve as afilter for attenuating signals at frequencies below the field frequency,said second and fourth resistors providing a D. C. signal path and saidsecond and third resistors forming a potentiometer to determine theratio of the D. C. and A. C. components of the signals transmitted bysaid channel, whereby upon the application to said cathode and controlelectrode of signals having D. C. and A. C. components signals areobtained between ground and the junction of said second capacitor andfourth resistor in which signals at frequencies between the fieldfrequency and 1 cycle per second are attenuated.

3. A television receiver according to claim 2 wherein said signalchannel has an attenuation versus frequency curve having maximumattenuation corresponding to a frequency of 1 to 3 cycles per second.

4. A television receiver including a picture reconstituting deviceoperating at line and field frequencies, a signal channel connecting thesignal input of said receiver to said device, said channel including anelectron discharge tube having a grounded cathode, a control electrodeand an anode, an alternating current path connected to said tube forpassing signals of field and higher frequencies, a direct current pathconnected to said tube for passing signals of zero frequency, saidalternating current path and said direct current path comprising a pairof resistors connected in series between said anode and a positivesupply terminal, and a first capacitor connected between the junction ofsaid resistors and ground, a second capacitor having one electrodeconnected to said control electrode, third and fourth resistors eachhaving one terminal connected to the respective electrodes of saidsecond capacitor, a third capacitor, the other terminals of said thirdand fourth resistors being connected to one electrode of said thirdcapacitor, the other electrode of said third capacitor being grounded, afourth capacitor having one electrode connected to said anode, a fifthresistor connected to the other electrode of said fourth capacitor andground, and a sixth resistor inshunt with said fourth capacitor, saidsecond resistor and first capacitor forming a filter and' said thirdresistor and third capacitor forming a filter, said filters beingproportioned to attenuate signals at frequencies above 1 cycle persecond upon the application of television signals between ground and thejunction of said third resistor and said second capacitor, and saidfourth capacitor and fifth resistor being proportioned to attenuatesignals below the field frequency, whereby in the signals set up betweenground and the ungrounded end of said fifth resistor signals atfrequencies between the field frequency and the frequency of 1 cycle persecond are attenuated.

5. A television receiver including a picture reconstituting deviceoperating at line and field frequencies, a signal channel connecting thesig nal input of said receiver to said device, said channel including anelectron discharge tube having a grounded cathode, a control electrodeand an anode, an alternating current path connected to said tube forpassing signals of field and higher frequencies, a direct current pathconnected to said tube for passing signals of zero frequency, saidalternating current path and said direct current path comprising firstand second resistors connected in series between said anode and apositive supply terminal, a first capacitor connected between thejunction of said first and second resistors and ground, third and fourthresistors connected between said anode and ground, a second electrondischarge tube having a cathode, a control electrode and an anode, fifthand sixth resistors connected in series between the cathode of saidsecond tube and ground, a second capacitor having one electrodeconnected to said anode and the other electrode connected to the controlelectrode of said second tube, a seventh resistor connected between thecontrol electrode of said second tube and the junction of said fifth andsixth resistors, and a third capacitor connected between the cathode ofsaid second tube and the junction of said third and fourth resistors,said third resistor affording a D. C. path between the anode of saidfirst tube and. the junction of said third and fourth resistors and saidfirst resistor and'first capacitor being proportioned to form a filterfor attenuating signals at frequencies above 1 cycle per second, saidsecond capacitor, secondelectron discharge tube and third capacitoraffording an A. C. path between the anode of said first tube and thejunction of said third and fourth resistors, and said second capacitorand seventh resistor together with said third capacitor and fourthresistor being proportioned to form filter means for attenuating signalat frequencies below the field frequency, whereby upon the applicationto the cathode and control electrode of said first tube of signalshaving D. C. and A. C."

channel including an electron discharge tube, an alternating currentpath connected to said tube.

for passing signals of the field and higher frequencies, a directcurrent path connected to said tube for passing signals of zerofrequency, and means for attenuating those frequencies lying between 1cycle. per second'anck field; itequeneyi more. than other; frequenciessaidachamiet to substantially reduce. fading of; the; mean bri ht: nessof the reconstituted picture due to television signals reflected frommoving objects.

7. A television receiver including/a picture 1:e:.- constituting deviceoperating. at. line and; field: frequencies; a signal channelconnecting, the; siga nal input .of said receiver; to said device, saidchannel including an electron discharge Whe,3n alternatin current pathconnected-- to. saidtube and including first attenuating means'iorattenn: ating signals the. more the lower the signal free.- quency and adirect current path including.see-. 0nd attenuating meansforattenuatingv signals the. more the higher the signal frequency, said8;. A, telenisien rece v r according to. laim 1, a d first and secondettnuatins. means; ein proportioned to, attenuate frequencies between thefield fr quency and; a frequency of 1 cycle p secondmore; than otherfrequencies.

CHARLES LESLIE FAUDELL,

Beferenges Cited in the. file of this patent UNITED STATES PATENTS.

Number Name Date 2,093,665 Tellegen Sept. 21, 1937' 2,223,982 Bedford'Dec. 3-, 1940 2,269,001 Blu nlein Jan. 6; 1942 233L973 White Dec. 2,1.9%? 23184352 Rose Oct. ll, 1949 2;,503L50' Aususfiad PI- 9.

BAT NEE Number Country Date 505,899 Great Britain May- 15, 1939

